The invention relates to a rotary actuator, particularly for controlling a throttle cross-section in a line carrying operating fluid for an internal combustion engine.
An electromagnetic rotary actuator is known comprising an actuator motor having a stator which is fixed with respect to a housing in which the motor is located and a rotatable armature. Either the armature or the stator has opposing permanent magnet segments arranged symmetrically with respect to the axis of rotation. The armature or stator not having the permanent magnet segments has field windings through which current can flow to energize the rotary actuator. A magnetically acting contactless restoring element is also provided located in the field of at least one of the permanent magnets. From JP-GM-GM 60-88044, such a rotary actuator is already known which has a magnetic restoring element which, when the power supply to the motor actuator fails, moves the armature of the rotary actuator into a defined rest position. Apart from the housing-fixed permanent magnets, the known restoring element consists of two further permanent magnets connected to the armature. Due to the small torque gradient in the rest position, this leads to a relatively small restoring force. On the other hand, the maximum torque of the restoring element opposing the control torque is undesirably high.